The planet Mercury is home to one of the largest impact basins in the solar system: the Caloris Basin. The Caloris Basin is about 1,500 km (932 miles) wide. The diameter of this impact basin is the length of 16,404 football fields (minus the end zones) placed end to end.

Mercury has color properties that would appear greyish-brown to the human eye. The color is controlled by the composition of the rocks that form the planet's surface, and the modification that they suffer as a result of impacts of all sizes (ranging in size from dust motes to tens or hundreds of kilometers). The surface of Mercury is also modified by energetic particles (mostly protons and electrons) from the solar wind.

The bright streaks that are prominent over much of Mercury's surface are called "crater rays." They are formed when an asteroid or comet strikes the surface. The tremendous amount of energy that is released in such an impact digs a big hole (crater) in the ground, and also crushes a huge amount of rock under the point of impact. Some of this crushed material is thrown far from the crater and then re-impacts the surface, forming the rays. Fine particles of crushed rock are more reflective than large pieces, so the rays look brighter. The space environment (dust impacts and solar-wind particles) causes the rays to darken with time.

Mountains on Mercury are formed by large impacts. Impact craters on Mercury larger than about 10 km in diameter (about 6 miles) usually have a mountain peak or ring of peaks in the center. The rims of large craters can also be considered as mountain ranges.

Yes. Mercury is one of the solid-surface bodies in our solar system. This group includes Mercury, Venus, Earth, the Moon, Mars and its moons, the asteroids, the moons of the outer planets, and Kuiper Belt objects. The outer planets Jupiter, Saturn, Uranus and Neptune are gas giants. They do not have solid surfaces that a person or robotic lander could stand or land on.

Jupiter's famous Red Spot is a storm that has been going on for at least several hundred years. The Red Spot is roughly 30 thousand km across in the East-West direction. Mercury's diameter is about 4,880 km, and Earth's diameter is about 12,700 km. So the Great Red Spot is much larger than the whole planet Mercury (and the Earth)!

Mercury's surface gravity is about 38% of that on Earth. Coincidentally, Mercury has nearly the same surface gravity as does Mars. The height that you can jump is proportional to the reciprocal of the gravity, so on Mercury or Mars you could jump (1.0/0.38) = 2.6 times higher than you could on Earth.

A human mission to Mercury is possible, but it would be extremely complicated and expensive. For example, just to get there takes a long time (MESSENGER needed six years). The travelers would need to take supplies (food, water, oxygen) for the six-year journey, and for the six-year return trip, plus supplies for whatever length of stay was planned on the surface. Carrying so much weight means that very large rockets would be needed (keep in mind that you would need to carry rocket fuel for the return trip, too).

The conditions on the surface of Mercury are very harsh, and space suits and habitats would need to be designed to withstand the high daytime temperatures and extremely cold nighttime temperatures. I would love to do geological field work on Mercury, but it will probably be many decades or even centuries before humans visit the surface of the innermost planet.